A Dynamic Voltage-Based Current Estimation Technique for DC Motor Speed Control Applications

Precise operation and control of electric drives in industrial applications, e.g., e-mobility, involve power electronic converters using feedback regulators connected to system state sensors. Typically, the torque of electric motors is directly related to current, and hence this necessitates accurate current sensing. An embedded controller used for a high-frequency drive application requires high bandwidth current sensors followed by high-resolution analog-to-digital converters (ADCs) for feedback regulation, which reflects on the cost and component count of the overall system. Current sensor-less estimation approaches provide an alternate possibility to mitigate the above drawbacks. This letter investigates a voltage-based current estimation approach for speed control of dc motor systems. The estimation of current utilizes only varying shunt (voltage) measurements, which can have dynamic variation, to estimate motor current without using high bandwidth current sensors and high-speed ADCs. Incorporating this estimation approach successfully achieves precise speed control of dc motor systems, demonstrating a cost-effective and component-efficient alternative to traditional high-bandwidth current sensing methods. The estimate of the current obtained can be incorporated with a digital control system for motor control. The theory and implementation of the proposed technique have been presented in the paper using a laboratory test-bed of a dc-motor with an FPGA-based controller.